Strapless breathing masks consisting of a strapless valve body, a window frame and a window shield, are worn in conjunction with a protective helmet. The breathing mask is normally secured to the protective helmet by a plug-in type connection. A typical example of such a strapless breathing mask is provided in U.S. Pat. No. 4,926,854, the disclosure of which is incorporated herein by reference, which patent is assigned to the same assignee as the present invention. It would be desirable to provide a means by which strapless breathing masks, designed only for use with a protective helmet, could be adapted to be worn without the helmet.